A polarizing film of a liquid crystal display (hereinafter abbreviated to as “LCD” when appropriate) is often treated to provide with a low refractive index layer for preventing or minimizing mirroring. An enhanced antireflection performance is required especially for a polarizing film of LCD used in the fields. For this requirement, a low refractive index layer comprised of a multilayer film or a single layer film is formed on a base film for a polarizing film.
The multilayer film for a low refractive index layer includes, for example, a multilayer film comprising a film of a relatively high refractive index and a film of relatively low refractive index, laminated in this order (for example, see Japanese Unexamined Patent Publication [hereinafter referred to as “JP-A”] No. H4-357134).
The process for forming a film includes, for example, a sol-gel process, a vacuum deposition process, a sputtering process and a chemical vapor deposition process. These processes comprise a step of exposing to a high temperature or placing in vacuum. At a high-temperature exposing step, a resin base film is liable to be distorted or modified and optical properties thereof tend to be varied. Thus, an antireflection film having desired properties is difficult to make. In a vacuum film-forming process, gas is inevitably released from a base resin material in a vacuum apparatus and thus, a high degree of vacuum is difficult to obtain, and an antireflection film having desired properties is difficult to make.
In the case when a low refractive index layer is comprised of two or more films, two or more coating operations for forming films are required and therefore the film-forming process is troublesome and costly. Further, the film thickness is difficult to control and therefore the desired low light reflection is difficult to attain.
As a process for forming a low refractive index layer comprising a single layer film, there have been proposed a process wherein a metal oxide film comprising multi-metal ingredients is formed on a glass pane by a sol-gel process, the metal oxide film is heated to be thereby separated into two phases, and then the film is subjected to etching by using hydrofluoric acid whereby the film is rendered porous due to difference of the etching rate of the two phases (see, for example, S. P. Mukherjee et al, J. Non-Cryst. Solids. Vol. 48, p 177(1982)), and a process wherein a composite film comprised of magnesium oxide and carbon dioxide is formed by a solo-gel process, and then, the composite film is exposed to a fluorine-containing gas at a high temperature whereby oxygen is substituted by fluorine (see, for example, J. H. Simmons et al, J. Non-Cryst. Solids, Vol. 178, p 166(1994)).
JP-A 2002-328,202 describes a process for making a low reflective resin base material wherein a surface of a resin base material is coated with a coating liquid containing at least one kind of organic silicon compound comprising an amino group-containing organic silicon compound, or its hydrolyzed product; the coating liquid is dried to form a first film on the resin base material; and then a silicon dioxide film having a refractive index of not larger than 1.40 and having a rough surface is formed on the first film. It is described in this patent publication that the films can be formed at a low temperature and at a time with enhanced adhesion onto the entire surface of the resin base material at a low temperature.
However, in the case when the low reflective resin base material described in the above-mentioned patent publication is applied to a liquid crystal device, the resulting liquid crystal device tends to exhibit poor visibility, i.e., small luminance, and a low contrast. Therefore, improvement of these properties is eagerly desired.